Systems and methods for the production of contact lenses

ABSTRACT

An apparatus for spin casting lenses includes a rotatable tube, the rotatable tube defining a longitudinal cavity, wherein the longitudinal cavity is configured to receive molds. According to one exemplary embodiment, the rotatable tube is made of metal and includes a plurality of apertures configured to permit the transmission of actinic radiation.

BACKGROUND ART

In recent decades, contact lenses have become a preferential alternativeto other eyesight correction methods. Due to their increased popularity,it has become mandatory that contact lenses be manufactured on a largescale in order to meet consumer demand. Further, these lenses arerequired to be precision manufactured with low tolerances in order toprovide a suitable and effective corrective lens.

Spin casting has been utilized as a method of producing contact lenses.However, traditional spin casting methods are disadvantageous forseveral reasons as will be discussed below, and have not readily beenemployed in the mass-production of contact lenses.

To begin, the polymerization casting of axially symmetrical articles,such as contact lenses, may be performed by using a spin castingprocess. In this process, a controlled quantity of a polymerizableliquid is placed into an open mold, which is then rotated about itsvertical axis at a rotational speed sufficient to produce a centrifugalforce that causes a radially outward displacement of the polymerizableliquid. By maintaining a controlled rotation rate, the centrifugal forcecaused by the rotation will cause the polymerizable liquid to adopt agenerally concave shape. Once the polymerizable liquid has attained anequilibrium shape, polymerization of the liquid can be effected by anysuitable means, such as heat or exposure to actinic radiation (i.e.ultraviolet light) so as to produce a solid polymeric contact lens.

The open mold used in a spin casting process is typically characterizedby an outer cylindrical wall and a mold comprising an exposed concavemolding cavity. The shape of the molding cavity will typically definethe shape of the front surface of the finished contact lens, and maycontain such desired elements as lenticulating curves, toric curves,non-spherical curves and other such features or shapes aimed atinteracting with the eye, its optical processes, or eyelids in apredetermined manner.

The shape factor of the posterior or back surface of the lens isdetermined predominantly by the angular speed of rotation, as well asother factors such as the surface tension of the polymerizable liquid,and the acceleration due to gravity.

The polymerizable liquid utilized in the spin casting process istypically one in which the polymerization reaction can be triggered byan external factor such as heat or actinic radiation (i.e. ultravioletlight), and is therefore most commonly utilized in connection with asystem that undergoes a free radical polymerization reaction. Typicallythese systems will include a monomer, or mixture of monomers based onacrylic or methacrylic acid, along with a free radial polymerizationinitiator. However, pre-polymerized materials such as solvent-basedmaterials may also be applied in a spin casting system.

To avoid the inhibiting effects of atmospheric oxygen during thepolymerization process, the molds and polymerizable liquid aremaintained, at least initially, in an inert gas atmosphere of, forexample, nitrogen or argon. The use of an external trigger for thepolymerization allows for the polymerizable liquid to attain itsequilibrium shape under rotation prior to the onset of polymerization,and also to allow time for any oxygen present within the mold ordissolved in the polymerizable liquid to diffuse away from thepolymerizable liquid.

During the actual mass production of contact lenses, the individualmolds can be arranged in a carousel or in a vertical stackconfiguration. The carousel arrangement is rather complex and quitelarge with respect to the size of the molds. It requires that each moldbe individually rotated on its own separate vertical axis. It isreported that the carousel arrangement suffers from the disadvantages ofrequiring excess inert gas to eliminate the inhibiting effect of oxygen(in the ambient environment) present during the polymerization reaction.The use of excess inert gas during the polymerization of the monomericreactants causes the entrainment of monomer in the form of vapors andthe subsequent deposition and/or polymerization of the monomer on thesurrounding objects, and, in particular, the equipment utilized by thesystem. Further information is set forth in Method of CentrifugallyCasting Thin Edged Corneal Contact Lenses, U.S. Pat. No. 3,660,545 toOtto Wichterle (filed Oct. 24, 1963) (issued May 2, 1972), the fulldisclosure of which is incorporated herein by reference in its entirety.

In the vertical stack arrangement a rotatable polymerization tube havingan internal, generally circular, cross-sectional geometry is adapted toreceive, at one end of the tube, a plurality of generally circular moldswhich become seated to one another in the tube, each mold containing thepolymerizable liquid reactants in their individual mold cavities. Thepolymerization tube, or rotatable tube, can be manufactured so that itsinternal diameter generally matches the external diameter of theindividual molds so as to provide an interference fit. More preferably,the rotatable tube can contain ridges or similar features so as tofacilitate a multiple point contact with the individual molds. Thislatter arrangement allows for the molds to rotate with the rotatabletube, and also to allow for the passage of inert gas through therotatable tube and past the individual molds. Suitable prior art designsfor the rotatable tube are disclosed in Device and Method forCentrifugally Casting Articles, U.S. Pat. No. 4,517,138 to David L.Rawlings et al. (filed May 2, 1983) (issued May 14, 1985) (hereinafter“'138 Patent”).

One typical prior art arrangement for the production of lenses by spincasting is that taught by the '138 Patent. In this design, monomer dosedmolds are fed, one by one, into the top of a rotatable tube comprisingtwo zones, a conditioning zone and a polymerization zone. Typically therotatable tube contains a plurality of dosed molds, so that therotatable tube is essentially full of molds. As each new mold isintroduced into the rotatable tube conditioning zone, a fully cured moldis ejected from the bottom of the polymerization zone.

By this means, the number of molds within the rotatable tube remainsconstant, with individual molds progressing slowly through first theconditioning zone, and then the polymerization zone. This arrangementallows the polymerizable liquid within each mold to attain itsequilibrium meniscus shape before entering the polymerization zone,wherein polymerization may be initiated. This arrangement, whileallowing for the continuous curing of contact lenses, is not without itsissues.

Predominant among these issues is line clearance. Contact lenses areproduced with a range of differing parameters, most notably the spherepower. A typical power range for a contact lens offered for sale will beat least +4.00 diopters to −8.00 diopters, in 0.25 diopter steps, whichrepresents 49 individual designs, or stock keeping units (SKU). In orderto switch production from one SKU to a second SKU, it is necessary toclear all partially and fully polymerized product from the rotatabletube, since to change SKU it is necessary to either change the molddesign and/or the rotational speed of the rotatable tube.

Typically this line clearance is achieved by adding mold blanks (forinstance empty molds, or cylindrical plugs) into the top of therotatable tube in place of the dosed molds, and continuing the spinningprocess until all the product is ejected from the polymerization zone.Once the required changes to effect the change of SKU have beencompleted, dosed molds can again be added one by one into the rotatabletube, with the mold blanks being ejected from the bottom of thepolymerization zone until all the blanks have been cleared. This lineclearance naturally can take some time, and essentially represents aperiod of reduced productivity.

The problems of line clearance are compounded when toric lenses aremanufactured. Toric lenses are used to correct those who have an opticaldefect called astigmatism. Astigmatism causes blurred vision due to theinability of the optics of the eye to focus a point object into a sharpfocused image on the retina. This may be due to an irregular or toriccurvature of the cornea or lens. With a toric lens, a typical powerrange would be with sphere powers over the range +4.00 diopters to −8.00diopters, in 0.25 diopter steps, with at least 1 cylinder power offeredin at least 6 axes, representing 294 individual SKU's.

Line clearance presents further problems if a temporary line stoppage isnecessary. Should a manufacturing parameter deviation create a temporaryline interruption, the full line must be cleared prior to troubleshooting or restarting. The very nature of a continuous flow systemdictates that molds can only be ejected or reintroduced at a standardpart rate. The larger or longer the line, the longer clearance time willbe required.

The problems of line clearance can be removed if the spinning process isrun as a batch or semi batch process. In this process, the rotatabletube is initially filled with dosed molds in one operation. Therotatable tube is then rotated at the desired rotation speed in order toallow the polymerization mixture contained within each mold to attainits equilibrium shape. Then polymerization is initiated by exposure to apreferred means of radiation. Ultraviolet polymerization is stronglypreferred in batch processing as it allows almost instantaneousswitching from zero exposure to full exposure, whereas a thermalinitiation would require both heat-up and cool-down periods. The overalllens production cycle in a batch spin casting process will thereforerequire less time, and, consequently, be more efficient when usingultraviolet polymerization.

However, in order to utilize ultraviolet initiation in spin casting, therotatable tubes are limited to being constructed from a materialtransparent to the passage of ultraviolet light. Further, the materialused in the construction of the rotatable tubes must not be subject tothe deleterious effects of prolonged ultraviolet exposure which maycause, for example, discoloration or mechanical degradation. For thisreason, most rotatable tubes are made from glass.

While glass is an efficient material for use in spin casting in terms ofUV transmissibility, the spin tube must also be able to both present anaccurate and straight inner bore for the molds and must spin around itsown vertical axis with minimal run out of polymerizable liquid andminimal vibration within the system. To achieve these objectivesutilizing a glass rotatable tube is not without its challenges. Firstly,glass is not conducive to accurate machining. In order to accuratelyform the inner bore of the rotatable tube, a hot blank glass rod must bedrawn onto a metal former. See, e.g., Method of Forming Precision BoreGlass Tubing, U.S. Pat. No. 2,458,934 to Everett Samuel James (filedNov. 22, 1941) (issued Jan. 11, 1949). This process is tedious and timeconsuming, and may produce a tube having an inner bore that containsflaws or is otherwise imprecise.

Secondly, the glass rotatable tube must be mounted accurately intobearings at the top and bottom of the tube. Typically this is achievedby grinding a taper onto either end of the tube. Once the tube has beenprovided with tapers, the tube may be mounted into the bearings. Thebearings must also be provided with a means for adjusting the rotatabletube so that the axis of rotation is exactly along the centerline of theinner bore (i.e. to eliminate “run-out”).

Further, since glass is susceptible to brittle failure, it cannot beexposed to high tensile stresses such that the bearing mountings shouldnot exert undue compressive force, or any excess shear forces whileadjusting run-out. This precludes the use of pre-loaded high-speedbearings and typically necessitates frequent tube alignment adjustmentsduring manufacturing.

Still further, glass tubes are susceptible to variational influences andmay exhibit some lack of continuity from the top to the bottom of thetube during the spinning process. A certain amount of transient flexuremay adversely affect the accuracy of individual lenses being spun withinthe tube. Potential inhomogeneity within the glass itself may alsocontribute to varying and disparate amounts of ultraviolet lightreaching the mold parts within the tube. If this were to occur throughthe vertical axis of the tube, certain mold parts within the tube mayreceive a variable level of UV radiation with possible deleteriouseffects.

Finally, when utilizing the prior art glass tubes in a spin castingsystem, the glass tubes are subject to undesirable vibrations. Thesevibrations in the glass tube are due to the inability to maintain asufficiently rigid connection between the glass tube and the bearingmountings. Vibrations within a system utilizing a glass tube maygenerate a product that lacks sufficient precision (e.g. a contact lenswith undesirable imperfections or defects).

What is needed is an apparatus, a system, and a method of mass-producingcontact lenses via spin casting that overcomes the above-mentionedfailings of prior art systems.

CITATION LIST Patent Literature

-   PTL 1: U.S. Pat. No. 3,660,545-   PTL 2: U.S. Pat. No. 4,517,138-   PTL 3: U.S. Pat. No. 2,458,934

SUMMARY OF INVENTION

According to one exemplary embodiment, an apparatus for spin castinglenses comprising a rotatable tube, the rotatable tube defining alongitudinal cavity, wherein the longitudinal cavity is configured toreceive molds. According to one exemplary embodiment, the rotatable tubeis made of a stable non-glass material such as metal.

According to another exemplary embodiment, a method of centrifugallycasting a lens comprising providing a first rotatable tube, introducingat least one mold into the internal bore of the first rotatable tube,the mold containing a polymerizable liquid, partially curing thepolymerizable liquid in the first rotatable tube, removing the mold fromthe first rotatable tube, providing at least one second curing device,introducing the mold into the second curing device, and completing thecuring of the polymerizable liquid in the second curing device.

According to yet another exemplary embodiment, a system for spin castinga lens comprising a first rotatable tube, the first rotatable tube beingconfigured to partially cure a polymerizable liquid contained in atleast one mold; and at least one second curing device, the second curingdevice being configured to finalize the curing of the polymerizableliquid contained in the mold.

According to yet another exemplary embodiment, a system for spin castinga lens, comprising a housing, a first rotatable tube disposed within thehousing, at least one set of bearings mounted between the housing andthe first rotatable tube, and a drive system for rotating the firstrotatable tube.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings illustrate various embodiments of theprinciples described herein and are a part of the specification. Theillustrated embodiments are merely examples and do not limit the scopeof the claims.

FIG. 1 is a cross-sectional view of a mold according to an embodiment ofthe present exemplary system and method.

FIG. 2 is a cross-sectional view of a mold according to anotherembodiment of the present exemplary system and method.

FIG. 3 is a schematic view of the mold of FIG. 2 according to anembodiment of the present exemplary system and method.

FIG. 4 is a cross sectional top view of the mold of FIG. 1 in removableengagement with a rotatable tube according to an embodiment of thepresent exemplary system and method.

FIG. 5 is a cross sectional top view of the mold of FIG. 2 in removableengagement with a rotatable tube according to an embodiment of thepresent exemplary system and method.

FIG. 6 is a schematic view of a rotatable tube according to anembodiment of the present exemplary system and method.

FIG. 7A is a schematic view of a rotatable tube including an apertureaccording to an embodiment of the present exemplary system and method.

FIG. 7B is a cross-sectional view of the rotatable tube of FIG. 7Aaccording to an embodiment of the present exemplary system and method.

FIG. 8A is a schematic view of a rotatable tube including a plurality ofapertures according to an embodiment of the present exemplary system andmethod.

FIG. 8B is a cross-sectional view of the rotatable tube of FIG. 8Aaccording to an embodiment of the present exemplary system and method.

FIG. 9A is a schematic view of a rotatable tube including a plurality ofrectangular apertures according to an embodiment of the presentexemplary system and method.

FIG. 9B is a cross-sectional view of the rotatable tube of FIG. 9Aaccording to an embodiment of the present exemplary system and method.

FIG. 10A is a schematic view of a rotatable tube including a pluralityof circular apertures according to an embodiment of the presentexemplary system and method.

FIG. 10B is a cross-sectional view of the rotatable tube of FIG. 10Aaccording to an embodiment of the present exemplary system and method.

FIG. 11A is a schematic view of a rotatable tube including a pluralityof diamond-shaped apertures according to an embodiment of the presentexemplary system and method.

FIG. 11B is a cross-sectional view of the rotatable tube of FIG. 11Aaccording to an embodiment of the present exemplary system and method.

FIG. 12A is a cross-sectional view of a portion of the rotatable tube ofFIGS. 10A and 10B including a plurality of tapered apertures accordingto an embodiment of the present exemplary system and method.

FIG. 12B is a cross-sectional view of a portion of the rotatable tube ofFIGS. 11A and 11B including a plurality of tapered apertures accordingto an embodiment of the present exemplary system and method.

FIG. 13 is a block diagram of a contact lens manufacturing systemaccording to an embodiment of the present exemplary system and method.

FIG. 14 is a cross-sectional view of a rotatable tube including moldretention means according to an embodiment of the present exemplarysystem and method.

FIG. 15 is a flow chart of a multi-stage curing process according to anembodiment of the present exemplary system and method.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present systems and methods. It will be apparent,however, to one skilled in the art that the present systems and methodsmay be practiced without these specific details. Reference in thespecification to “an embodiment,” “an example” or similar language meansthat a particular feature, structure, or characteristic described inconnection with the embodiment or example is included in at least thatone embodiment, but not necessarily in other embodiments. The variousinstances of the phrase “in one embodiment” or similar phrases invarious places in the specification are not necessarily all referring tothe same embodiment.

The present exemplary system and methods are configured for the spincasting symmetrical or asymmetrical articles. More specifically, thepresent exemplary systems and methods are configured for the productionof contact lenses including a rotatable tube adapted for accommodating aplurality of molds within the rotatable tube, wherein the rotatable tubemay be constructed from a substantially opaque material containingapertures or sections of non-opaque material configured to selectivelyallow the passage of actinic radiation to facilitate the polymerizationor photochemical cross-linking of material dispersed in the molds. Asused in the present specification, the term “aperture” shall beinterpreted broadly as including any portion of a rotatable memberconfigured to selectively control the amount of light admitted withinthe member.

Molds

FIG. 1 is a cross-sectional view of a mold (100) according to anembodiment of the present exemplary system and method. The mold (100)may include a cylindrical sidewall (110), to which a molding cavity(120) is internally connected. The concave surface of the molding cavity(120) serves to mold the convex surface of the article being molded(e.g. the convex or outer surface of a contact lens).

The molding cavity (120) is connected to the cylindrical wall (110) ofthe mold (100). The connection between the molding cavity (120) and thecylindrical wall (110) may be any means of connection such that therelative position between molding cavity (120) and the cylindrical wall(110) cannot change during a specified length of time or throughout apredetermined operation. In one exemplary embodiment, the connectionbetween the molding cavity (120) and the cylindrical wall (110) may bemade by welding the molding cavity (120) to the cylindrical wall (110).In another embodiment, the connection between the molding cavity (120)and the cylindrical wall (110) may be made by forming the molding cavity(120) and the cylindrical wall (110) out of a single piece of material,such as in an injection molding process. In yet another embodiment, themolding cavity (120) and the cylindrical wall (110) may be removablycoupled. For example, mechanical means for removably connecting themolding cavity (120) to the cylindrical wall (110) may be provided.

The mold (100) may further include a number of engagement apertures(130). The mold (100) may be introduced as a stacked column of molds ina rotatable tube, as will be discussed in more detail below. Whenentering the rotatable tube, the mold (100) may be secured with respectto the horizontal axis of the rotatable tube via the engagementapertures (130). For example, mechanical means may be provided to engagethe engagement apertures (130). In one exemplary embodiment, theengagement apertures (130) may be used to secure a number of molds (100)introduced into the rotatable tube.

In yet another embodiment, the engagement apertures (130) may be used tosecure only the bottom mold (100). In this embodiment, the remainingmolds (100) may rest on top of, and be supported by, the bottom mold(100). Further, in this embodiment, the engagement apertures (130) ofthe remaining molds (100) may provide for diffusion of an inert gasthroughout the rotatable tube and between individual molds (100) as willbe discussed in more detail below.

Turning now to FIGS. 2 and 3; FIG. 2 is a cross-sectional view of a mold(200) according to another exemplary embodiment of the present exemplarysystem and method, and FIG. 3 is a schematic view of the mold (200) ofFIG. 2 according to an exemplary embodiment of the present exemplarysystem and method. In the embodiment of FIGS. 2 and 3, the connectionbetween the molding cavity (120) and the cylindrical wall (110) may bemade by a number of radial spokes (210). As is shown in FIG. 3, threeradial spokes (210) connect the molding cavity (120) and cylindricalwall (110). However, any number of radial spokes (210) may be utilized.Further, as shown in FIGS. 2 and 3, the radial spokes (210), moldingcavity (120), and the cylindrical wall (110) may be formed from a singlepiece of material, such as in a single injection molding process.However, the radial spokes (210), molding cavity (120), and thecylindrical wall (110) may alternatively be formed from differentmaterials and as separate elements. Further, the molding cavity (120)and the cylindrical wall (110) of the embodiment of FIGS. 2 and 3 may beremovably coupled. For example, mechanical means for removablyconnecting the molding cavity (120) to the cylindrical wall (110) may beprovided.

Interface Between the Molds and the Rotatable Tube

FIG. 4 is a cross sectional top view of the mold (100) of FIG. 1 inremovable engagement with a rotatable tube (400) according to anembodiment of the present exemplary system and method. The mold (100)may be placed inside a rotatable tube (400) as will be discussed in moredetail below. In order to ensure that the mold (100) remains secureinside the rotatable tube (400), the mold (100) may further include aninterface ring (410) for retaining the mold (100) and the rotatable tube(400) in symmetrical rotation. The interface ring (410) may include anumber of voids (420) that run longitudinally, or, in other words,parallel with respect to the z-axis of the mold (100) and rotatable tube(400) as depicted in FIG. 4. The voids (420) may be formed in theinterface ring (410) by any manner as is known in the art. For example,in one embodiment, the interface ring (410) may be cast as a singlepiece which defines the voids (420). In another embodiment, theinterface ring (410) may be formed as a single piece, and the voids(420) may be removed from the interface ring (410) by drilling, boring,etching, etc.

Further, the rotatable tube (400) may include a number of protrusions(430) on the interior wall of the rotatable tube (400). The protrusions(430) may run longitudinally along the interior of the rotatable tube(400), or, in other words, parallel with respect to the z-axis of therotatable tube (400) as depicted in FIG. 4.

The protrusions (430) of the rotatable tube (400) and the voids (420) ofthe interface ring (410) may form an interference fit, and may be heldin place by frictional forces. The interference fit may be such thatwhen the rotatable tube (400) is rotated, the interface ring (410), and,thus, the mold (100) remains in symmetrical rotation with the rotatabletube (400). The voids (420) and protrusions (430) may be of any shape orform. For example, as depicted in FIG. 4, the border between the voids(420) and protrusions (430) form a semicircular line. However, any shapethat creates a sufficiently close-fitting interface between therotatable tube (400) and the interface ring (410) is within the scope ofthe present exemplary system and method. For example, a void andprotrusion pair that forms an angular line between the rotatable tube(400) and the interface ring (410) may also be used. One importantcontrol criteria is that the mould/tube relationship minimizescircumferential run out aspects and maintaining a controllable spinvariant that is consistent with both the desired input speed and theother moulds within the tube.

Further, any number of void and protrusion pairs may be formed betweenthe rotatable tube (400) and the interface ring (410). For example, FIG.4 depicts four void and protrusion pairs. However, any number of voidand protrusion pairs may be used. In yet another embodiment, the voids(420) may be formed in the rotatable tube (400), and the protrusions(430) may be formed on the interface ring (410).

FIG. 5 is a cross sectional top view of the mold (200) of FIG. 2 inremovable engagement with a rotatable tube (400) according to anembodiment of the present exemplary system and method. Similar to themold (100) of FIG. 4, the mold (200) of FIG. 5 may be placed inside arotatable tube (400) as will be discussed in more detail below. In orderto ensure that the mold (200) remains secure inside the rotatable tube(400), the mold (200) may further include an interface ring (410) forretaining the mold (200) and the rotatable tube (400) in symmetricalrotation. The interface ring (410) may include a number of voids (420)that run longitudinally with respect to the z-axis of the mold (200) androtatable tube (400) as depicted in FIG. 5. The voids (420) may beformed in the interface ring (410) by any manner as is known in the art.For example, in one embodiment, the interface ring (410) may be cast asa single piece which defines the voids (420). In another embodiment, theinterface ring (410) may be formed as a single piece, and the voids(420) may be removed from the interface ring (410) by drilling, boring,etching, etc.

The rotatable tube (400) may include a number of protrusions (430) onthe interior wall of the rotatable tube (400). The protrusions (430) mayrun longitudinally along the interior of the rotatable tube (400) withrespect to the z-axis of the rotatable tube (400) as depicted in FIG. 5.

The protrusions (430) of the rotatable tube (400) and the voids (420) ofthe interface ring (410) may form an interference fit, and may be heldin place by frictional forces. The interference fit may be such thatwhen the rotatable tube (400) is rotated, the interface ring (410), and,thus, the mold (100) remains in symmetrical rotation with the rotatabletube (400). The voids (420) and protrusions (430) may be of any shape orform. For example, as depicted in FIG. 4, the border between the voids(420) and protrusions (430) form a semicircular line. However, any shapethat creates a sufficiently close-fitting interface between therotatable tube (400) and the interface ring (410) is within the scope ofthe present exemplary system and method. For example, a void andprotrusion pair that forms an angular line between the rotatable tube(400) and the interface ring (410) may also be used.

Further, any number of void and protrusion pairs may be formed betweenthe rotatable tube (400) and the interface ring (410). For example, FIG.4 depicts four void and protrusion pairs. However, any number of voidand protrusion pairs may be used. In yet another exemplary embodiment,the voids (420) may be formed in the rotatable tube (400), and theprotrusions (430) may be formed on the interface ring (410).

In another embodiment, the molds (FIG. 1, 100; FIG. 2, 200) may beretained within the rotatable tube (400) via an active mechanical means.This exemplary embodiment will be explained in further detail below.

Rotatable Tube

FIG. 6 is a schematic view of a rotatable tube (400) according to anexemplary embodiment of the present exemplary system and method. Theexemplary rotatable tube (400) may, according to one exemplaryembodiment, include four zones: two bearing mounting zones (600), acuring zone (610), and at least one drive zone (620). Preferably thebearing mounting zones (600) are dispersed on either side of the curingzone (610). The drive zone (620) may be at one end of the rotatable tube(400), or between the curing zone (610) and one or more of the bearingmounting zones (600).

According to one exemplary embodiment, the rotatable tube (400) may beconstructed from a rigid, ideally non-brittle, material with a precisioninternal bore (630). The internal bore (630) of the rotatable tube (400)may provide for a minimal disparity in mold-to-bore fit with a number ofenclosed molds (FIG. 1, 100; FIG. 2, 200) such that the rotation of therotatable tube (400) causes synchronized rotation of the molds (FIG. 1,100; FIG. 2, 200) at the same angular speed as that of the rotatabletube (400) while maintaining the concentricity of the molds (FIG. 1,100; FIG. 2, 200) contained within the curing zone (610) with respect tothe longitudinal axis of the rotatable tube (400). This therebyeffectively ensures the production of a plurality of symmetrical orasymmetrical spun cast identical articles, when a photo-initiatedcomposition (e.g., a photochemically polymerizable orphoto-crosslinkable composition) contained within molds (FIG. 1, 100;FIG. 2, 200) is exposed to actinic radiation (e.g. ultraviolet light).

The rotatable tube (400) may, according to one exemplary embodiment, befabricated from a variety of materials. For example, the rotatable tube(400) may be made of ceramic, carbon fiber, Polytetrafluoroethylene(PTFE or Teflon), Polyetheretherketone (PEEK), or any other suitablerigid engineering material. Further, the rotatable tube (400) may bemade from metals such as, for example, stainless steel, brass, titanium,or aluminum. Generally, the rotatable tube (400) may be made of asufficiently strong material that is able to withstand torsional forcesapplied to the rotatable tube (400) when the rotatable tube (400) isrotated. The various attributes of the rotatable tube (400) of FIG. 6may also apply to other various embodiments of the rotatable tubediscussed herein.

Additionally, according to one exemplary embodiment, the internal bore(630) of the rotatable tube (600) may be reflective. The reflectiveproperty of the internal bore (630) may be achieved by applying areflective coating such as, for example, silver to the internal bore(630). In another exemplary embodiment, the reflective property of theinternal bore (630) of the rotatable tube (600) may be formed byproviding a rotatable tube (600) made of metal and polishing theinternal bore (630) such that the internal bore (630) becomessufficiently smooth to reflect radiant energy. For example, therotatable tube (600) may be made of stainless steel, wherein, when theinternal bore (630) of the stainless steel rotatable tube (600) ispolished or otherwise made sufficiently smooth, the internal bore (630)reflects radiant energy. Providing an internal bore (630) that reflectsradiant energy may allow for actinic radiation that enters the rotatabletube (600) to more uniformly initiate the photochemical polymerizationreaction of the polymerizable liquid contained within the molds (FIG. 1,100; FIG. 2, 200) of the rotatable tube (600), thus more perfectlycuring a particular contact lens.

FIGS. 7A-11B illustrate rotatable tubes (400) including aperturesaccording to several embodiments of the present exemplary system andmethod. In these exemplary embodiments, at least one aperture isprovided within the curing zone (FIG. 6, 610) to allow passage ofactinic radiation. As discussed above, a photo-initiated composition(i.e., a photochemically polymerizable or photo-crosslinkablecomposition) contained within molds (FIG. 1, 100; FIG. 2, 200) may becured via exposure to actinic radiation that enters in through theapertures. The apertures within the curing zone (FIG. 6, 610) may beopen, or filled with a material transparent to actinic radiation.

First, FIG. 7A is a schematic view of a rotatable tube (700) includingan aperture (710) according to an embodiment of the present exemplarysystem and method. The embodiment of FIG. 7A comprises a rotatable tube(700) containing a single aperture, wherein the aperture comprises alongitudinal slot (710). The longitudinal slot (710) extends the lengthof the curing zone (610), and is of uniform width. The width of thelongitudinal slot (710) may occupy a distance of 0.05 to 49% of theouter circumference of the rotatable tube (700). FIG. 7B is across-sectional view of the rotatable tube (700) of FIG. 7A. As isillustrated in FIG. 7B, the rotatable tube (700) has been rotated aquarter of a turn in order to better illustrate the longitudinal slot(710). The longitudinal slot (710) may be formed in the rotatable tube(700) by drilling, boring, etching, wire cutting, casting, or any othermethod. With regard to this and other embodiments of the rotatable tube,it is necessary to provide in the surface area of the rotatable tubewith a sufficiently large percentage of aperture space to allow asufficient amount of actinic radiation to enter the tube, thusincreasing the effective exposure of the polymerizable liquid containedwithin the molds (FIG. 1, 100; FIG. 2, 200) inside the rotatable tube.

FIG. 8A is a schematic view of a rotatable tube (800) including aplurality of apertures (810) according to an embodiment of the presentexemplary system and method. As illustrated in FIG. 8A, one means forincreasing the effective exposure of elements, and specifically molds(FIG. 1, 100; FIG. 2, 200) contained within the rotatable tube (800), toactinic radiation is to increase the number of apertures within thecuring zone (610) of the rotatable tube (800). In FIG. 8A, the rotatabletube (800) includes a plurality of longitudinal slots (810), with eachlongitudinal slot (810) being equal in length, and extending the lengthof the mold-containing portion of the rotatable tube (800). FIG. 8B is across-sectional view of the rotatable tube of 8A better illustrating theplurality of longitudinal slots (810). Preferably, the longitudinalslots (810) should be of equal width, and equally disposed about therotatable tube (800) so as to provide a consistent and uniformtransmission of actinic radiation to the interior of the rotatable tube(800). A sufficient amount of intermediary material (820) may also beleft between the longitudinal slots (810) so as to provide sufficienttorsional strength throughout the rotatable tube (800). In other words,the torsional strength of the rotatable tube (800) provides forsynchronized rotation of the molds (FIG. 1, 100; FIG. 2, 200) containedwithin the rotatable tube (800) at the same angular speed as therotatable tube (800), while maintaining the concentricity of the molds(FIG. 1, 100; FIG. 2, 200) with regard to the to the longitudinal axisof the rotatable tube (800).

Turning now to FIG. 9A, a schematic view of a rotatable tube (900)including a plurality of rectangular apertures (910) according to anembodiment of the present exemplary system and method is illustrated.FIG. 9B is a cross-sectional view of the rotatable tube of FIG. 9A. Thestaggering of the rectangular apertures (910) throughout the rotatabletube (900) may provide for a sufficiently robust rotatable tube (900)that is not subject to torsional distortions. Further, dependent orindependent of the potential torsional distortion of the rotatable tube(900), a vibrational mode may be established in which the walls of therotatable tube (9000 may flex outwards. This vibrational mode may resultin a loss of friction between the molds (FIG. 1, 100; FIG. 2, 200) andthe inner wall of the rotatable tube (900), or may allow the molds (FIG.1, 100; FIG. 2, 200) to rotate non-concentrically with respect to thelongitudinal axis of the rotatable tube (900). The staggering of therectangular apertures (910) in the rotatable tube (900) of FIGS. 9A and9B may provide for a sufficiently sturdy rotatable tube (900). This maybe accomplished by providing a sufficient amount of intermediarymaterial (920) as also addressed above in connection with FIGS. 8A and8B.

FIG. 10A is a schematic view of a rotatable tube (1000) including aplurality of circular apertures (1010) according to an embodiment of thepresent exemplary system and method. FIG. 10B is a cross-sectional viewof the rotatable tube (1010) of FIG. 10A. Similar to the previouslyaddressed embodiments, the rotatable tube (1000) of FIGS. 10A and 10Bincludes a plurality of circular apertures (1010) with a sufficientamount of intermediary material (1020) provided between the circularapertures (1010). In this embodiment, the percentage of intermediarymaterial (1020) may be further increased while still maintaining asufficient amount of circular apertures (1010) throughout the rotatabletube (1010) so as to provide a sufficient amount of actinic radiation topermeate throughout the rotatable tube (1010).

FIG. 11A is a schematic view of a rotatable tube (1100) including aplurality of diamond-shaped apertures (1110) according to anotherembodiment of the present exemplary system and method. FIG. 11B is across-sectional view of the rotatable tube (1110) of FIG. 11A betterillustrating the diamond-shaped apertures (1110). In the embodiment ofFIGS. 11A and 11B, the rotatable tube (1100) comprises a curing zone(610) containing a plurality of apertures (1110) disposed about thecuring zone (610). The apertures (1110) depicted in FIGS. 11A and 11Bare of a general diamond shape.

However, the apertures (710, 810, 910, 1010, 1110) may be any variety ofshapes, such as, for example, longitudinal slots, short slots, orcircles as illustrated in the above embodiments. The apertures (710,810, 910, 1010, 1110) may further include ovals, diamonds, triangles, orany combination of shapes. The apertures (710, 810, 910, 1010, 1110) maybe disposed in a staggered configuration throughout the curing zone(610) of the rotatable tube (1100) so as to allow even curing of themolds (FIG. 1, 100; FIG. 2, 200) contained within the rotatable tube(1100). In general, the shape of the apertures may be symmetric in boththe horizontal and vertical directions, and placed so that no side ofthe aperture lies in the x-y plane of the rotatable tube. The aperturesmay be designed to facilitate an even and homogenous distribution ofactinic radiation to the molds (FIG. 1, 100; FIG. 2, 200) containedwithin the curing zone (610). The use of non-uniform aperture shapes orboundaries of shapes may also be effectively used to ensure that UVhomogeneity occurs throughout the entire curing zone of the rotatabletube, irrespective of individual mold (FIG. 1, 100; FIG. 2, 200)placement within the curing zone of the rotatable tube. Variouswell-known means of optical clarification such as ray tracing may beused to optimize the aperture (910) shapes and boundaries.

FIG. 12A is a cross-sectional view of a portion of the rotatable tube ofFIGS. 10A and 10B including a plurality of tapered apertures accordingto an embodiment of the present exemplary system and method. Similarly,FIG. 12B is a cross-sectional view of a portion of the rotatable tube ofFIGS. 11A and 11B including a plurality of tapered apertures accordingto an embodiment of the present exemplary system and method. Asillustrated in FIGS. 12A and 12B, as well as throughout the variousembodiments discussed above, and other possible embodiments, theapertures (1010, 1110) may be wider towards the inside of the rotatabletube (1000, 1100) than the outside. In other words, the apertures (1010,1110) of the various embodiments may taper from the internal bore to theoutside surface of the rotatable tube (1000, 1100).

Specifically, in FIG. 12A, the rotatable tube (1000) of FIGS. 10A and10B may be provided with a plurality of circular apertures (1010) with adepth equaling the thickness of the rotatable tube (1000). An individualaperture (1010) may include two different radii; namely a smaller radius(1215A) located on the outer surface of the rotatable tube (1000), and alarger radius (1220A) located on the inner surface of the rotatable tube(1000).

Similarly, in FIG. 12B, the rotatable tube (1010) of FIGS. 11A and 11Bmay be provided with a plurality of diamond shaped apertures (1110) witha depth equaling the thickness of the rotatable tube (1100). Anindividual aperture (1110) may include two different sizes of diamondshapes; namely a smaller size (1215B) located on the outer surface ofthe rotatable tube (1100), and a larger size (1220B) located on theinner surface of the rotatable tube (1000).

By providing a tapered configuration within the apertures (1010, 1110),the apertures (1010, 1110) may provide greater illumination of thecontained molds (FIG. 1, 100; FIG. 2, 200), as well as reduce thephysical area of contact between the molds (FIG. 1, 100; FIG. 2, 200)and the internal bore of the rotatable tube (1000, 1100). Further, ithas been found that such an arrangement mitigates spillage ofpolymerizable liquid from the molds (FIG. 1, 100; FIG. 2, 200) whichwould otherwise contaminate the internal walls of the rotatable tube.Spillage of polymerizable liquid may lead to the molds (FIG. 1, 100;FIG. 2, 200) becoming adhered to the rotatable tube (1000, 1100), andcausing blockages at the end of the curing cycle when the cured partsare ejected from the rotatable tube (1000, 1100).

Any tendency for spilt monomer to adhere to the internal bore of therotatable tube may also be reduced by providing the rotatable tube witha lower energy surface (typically below 30 Dyne/cm), either by carefulchoice of material from which the rotatable tube is made of (i.e. PEEK,PTFE, etc.), or by applying to the internal bore of the rotatable tube ahydrophobizing surface treatment. The hydrophobizing surface treatmentmay include, for example, a suitable silane coupling agent (i.e.,octadecyltrimethoxysilane, dimethyl dichlorosilane, etc.). In anotherembodiment, a hydrophobizing surface may be achieved by plasmapolymerization of hydrocarbons such as methane onto the surfaces of therotatable tube.

While the present exemplary system has been described as including atube having any number of symmetrical orifices in the non-transparentmaterial, any combination of non-symmetrical orifices may also be used.Additionally, other configurations have been contemplated, according tothe teachings of the present exemplary system and method. For example,according to one embodiment, the rotatable tube (1000) may include asemi circular metal section with full metal sections at the bearingmounts while incorporating at least one transparent or translucentwindow medium that circumvents an “aperture”.

Contact Lens Manufacturing System

FIG. 13 is a block diagram of a contact lens manufacturing system (1300)according to an embodiment of the present exemplary system and method.The system (1300) may include a housing (1305) to house the rotatabletube (400). The housing (1305) may be hermetically sealed so as toprevent contamination from entering the area. Further, the housing(1305) may be hermetically sealed so that an inert gas may be introducedto the system. As discussed above, to avoid the inhibiting effects ofatmospheric oxygen during the polymerization process, the molds (FIG. 1,100; FIG. 2, 200) and polymerizable liquid are maintained in an inertgas rich, oxygen free atmosphere of, for example, nitrogen or argon. Theuse of an external curing means such as actinic radiation as an externaltrigger for the polymerization coupled with the anaerobic atmosphereprovided by the inert atmosphere allows for the polymerizable liquid toattain its equilibrium shape under rotation prior to the initiation ofpolymerization. The use of an inert gas within the system furtherprovides for sufficient time for any oxygen present within the mold ordissolved in the polymerizable liquid to diffuse away from thepolymerizable liquid.

Therefore, the housing (1305) surrounding the rotatable tube (400) mayinclude a means of providing an inert atmosphere within the housing(1305) and rotatable tube (400). The inert atmosphere within the housing(1305) may be accomplished, for example, by providing a number of inletports (1310) at either a single point into the space between therotatable tube (400) and the interior housing wall, or at a plurality ofpoints, arranged, either radially or longitudinally about the housing inorder to allow the passage of inert gas into the interior of the housing(1305). Thus, an inert gas may be introduced at either a single point inthe space between the rotatable tube (400) and the interior wall of thehousing (1305), or at a plurality of points, arranged either radially orlongitudinally about the housing (1305).

The inert gas introduced into the housing (1305) will be free to diffusethrough the apertures within the curing zone (610) of the rotatable tube(400). In one embodiment, the molds (FIG. 1, 100; FIG. 2, 200) containedwithin the rotatable tube (400) may contain castellations, cutaways,engagement apertures (FIG. 1, 130), or any number of other apertures inthe cylindrical sidewall to allow the passage of gas into the moldcolumn, as mentioned above. In another embodiment, the molds (FIG. 1,100; FIG. 2, 200) should be affixed to the cylindrical side wall of therotatable tube (400) via a plurality of radial spokes (210), asdiscussed above, thus allowing the longitudinal passage of inert gasthrough the column of molds (FIG. 1, 100; FIG. 2, 200).

At the same time, the use of excess inert gas during the polymerizationof the polymerizable liquid may cause the entrainment of monomer in theform of vapors and the subsequent deposition and/or polymerization ofthe monomer on the surrounding objects. In particular, the monomervapors may be deposited and/or polymerized on the equipment utilized bythe system (1300). The egress of the inert gas from the housing (1005)from either end of the rotatable tube (400) may be controlled via avariety of gas egress means. Generally, there may be provided a numberof inert gas egress ports (1315) for allowing a volume of inert gas toescape the housing (1305). For example, inert gas egress may beeffectuated by the use of plugs, iris valves, flap valves, plungers,etc. In one exemplary embodiment, inert gas egress from the rotatabletube (4000) may be restricted by placing a number of plugs (1315 a) atthe top and/or bottom of the rotatable tube (400) containing a column ofmolds (FIG. 1, 100; FIG. 2, 200), but allowing for gas egress in thearea juxtaposition to the curing zone (610). The plugs (1315 a) may becylindrical in shape and of identical outside diameter as the molds(FIG. 1, 100; FIG. 2, 200). Further, the plugs (1315 a) may be the sameheight as an individual mold (FIG. 1, 100; FIG. 2, 200). In a secondembodiment, gas egress from the top of the rotatable tube (400) may becontrolled with a flap valve, or an iris valve, while gas egress fromthe bottom may be controlled by suitable placement of a plunger rod usedto load molds (FIG. 1, 100; FIG. 2, 200) into the rotatable tube (400).

The walls of the hermetically sealed housing (1305) may be made of anymaterial. In one embodiment, the walls of the housing (1305) may be madeof glass thus providing for the introduction of actinic radiation to thesystem through the glass walls.

In another exemplary embodiment, the walls of the housing (1305) may bemade of a rigid material such as metal. The use of a precision-formedmetal housing provides for a secure and accurate stand-alone spin tubehousing. The use of such a housing and spin tube combination facilitatesthe quick change over of spin tubes for maintenance without requiringre-alignment of the spin tubes upon reinstallation. The walls of thehousing (1305) may further include windows for the transmission ofactinic radiation to the system. The window may be coated with ananti-reflection material in order to minimize radiation losses viasurface reflections within the housing (1305). In another exemplaryembodiment, specific anti-reflection coatings may be used to optimizethe transmission of particular wavelengths of radiation while reducingthe transmission of others.

Drive System for Contact Lens Manufacturing System

The rotatable tube (400) may be provided with a means for facilitatingsmooth rotation accurately about the longitudinal axis while minimizingany movement off axis, thus allowing the accurate concentric rotation ofthe molds (FIG. 1, 100; FIG. 2, 200) contained within the rotatable tube(400) about the longitudinal axis. This may be achieved by any meansknown in the art. For example, smooth longitudinal rotation may beachieved by engagement means (1320) such as, for example, bearingsmounted on the bearing mounting zones (600) of the rotatable tube (400).Preferably, the engagement means (1320) engage the rotatable tube (400)through a wall of the housing (1305) so as to fully enclose the curingzone (610) of the rotatable tube (400).

The drive zone (620) may be disposed at the bottom end of the rotatabletube (400), and may be located exterior to the housing (1305). A drivesystem (1340) may be provided within the drive zone (620) in order torotate the rotatable tube (400). In one exemplary embodiment, the drivesystem (1340) may include a drive pulley coupled to an electric motorvia a chain or belt drive. Preferably, the drive pulley may be larger indiameter than the rotatable tube (400), and may be constructed from ahigh-density material so as to increase the moment of inertia of therotatable tube assembly, thus providing for a more uniform angularvelocity.

In another exemplary embodiment, the drive pulley may be provided withcircumferential magnets, so as to magnetically couple the drive pulleywith a second driven pulley, thus allowing the mechanical separation ofthe rotatable tube (400) and the drive motor. By this means, therotatable tube (400) can be isolated from any vibrations induced by thedrive motor.

In yet another exemplary embodiment, and as depicted in FIG. 13, therotatable tube (400) may be driven directly. In this embodiment, thedrive zone (620) is fitted with a circumferential arrangement ofpermanent magnets (1325), and a means of assessing the angular velocityof the rotatable tube (400) such as a Hall Effect transducer (1345). TheHall Effect transducer (1345) determines the power dissipated to thedrive system (1340) by sensing the current provided to a load and usingthe device's applied voltage as a sensor voltage. The permanent magnets(1325) may be surrounded by a circular arrangement of drive coils(1330). Direct current may be provided to each drive coil (1330)sequentially, thus providing a brushless direct current motor. Thetiming of the provision of current to each coil (1330) is providedelectronically by the Hall Effect transducer (1345), thus allowing for ahighly accurate angular rotation.

Sources of Actinic Radiation for Contact Lens Manufacturing System

The housing (1305) surrounding the rotatable tube (400) may be providedwith a means for illuminating the contents of the rotatable tube (400)with actinic radiation. The means of illumination may be held within thehousing (1305), or external to the housing (1305), and can comprise anymeans of providing actinic radiation at a desired wavelength uniformlyover the length of the aperture-containing curing zone (610) of therotatable tube (400).

Generally, there may be provided a number of actinic radiation sources(1350) for producing actinic radiation. Examples of actinic radiationsources (1350) may be UV LED arrays, fluorescent tube lamps, or mercurydischarge lamps. In embodiments where the actinic radiation sources(1350) are located in the interior of the housing (1305), the actinicradiation may be directly provided to the polymerizable liquid containedwithin the individual molds (FIG. 1, 100; FIG. 2, 200) located withinthe rotatable tube (400).

In embodiments where the actinic radiation sources (1350) are externalto the housing (1305), the housing (1305) may include means for thetransmission of actinic radiation such as quartz or borosilicate glasswindows. In one exemplary embodiment, the windows may be anti-reflectioncoated in order to minimize radiation losses via surface reflections. Inanother exemplary embodiment, specific anti reflection coatings may beused to optimize the transmission of particular wavelengths of radiationwhile reducing the transmission of others.

In yet another exemplary embodiment, various combinations of radiationand radiation filters may be used in conjunction with each other toalter or amend various properties of the radiation entering therotatable tube (400), and thus change the polymerization conditionswithin the rotatable tube (400). The use of the various combinations ofradiation and radiation filters may be effected throughout the entireprocess or may be used judiciously at desired times throughout themanufacturing process.

In an exemplary embodiment, the use of high mass materials may be usedto facilitate a structurally robust housing (1305) and robust rotatingmembers that are less affected by drive born vibrations or rotationalfluctuations. In the present system, it is preferred that bothrotational stability (in all axes) and vibrational isolation areoptimized during the spinning process. Further, the rotatable tube(400), housing (1005), and drive may be constructed in a modular fashionso as to allow for easy replacement and maintenance.

In another exemplary embodiment, the arrangement of a number ofrotatable tubes (400) within a single rigid housing (1305) is possible.Arranging a number of rotatable tubes (400) within a housing (1305)facilitates a greater level of productivity without sacrificing accuracywithin each rotatable tube (400). Well-known and standard means of intertube spacing and part loading can be encompassed as part of the overallproduction process.

Retention of Molds in the Curing Zone

FIG. 14 is a cross-sectional view of a rotatable tube (400) includingmold retention means according to an embodiment of the present exemplarysystem and method. The molds (FIG. 1, 100; FIG. 2, 200) may be heldwithin the curing zone (FIG. 6, 610) by a variety of means. In oneembodiment, the molds, (FIG. 1, 100; FIG. 2, 200) may be constructed ofsuch a dimension so as to produce an interference fit with the innerwall of the rotatable tube (400), and may be held in place by frictionalforces, as discussed above.

Alternatively the molds (FIG. 1, 100; FIG. 2, 200) may be held in placeby an active mechanical means. In one embodiment, the molds (FIG. 1,100; FIG. 2, 200) may be introduced into the lower end of the rotatabletube (400) in the direction of arrow (1410) using a pusher rod. Themolds (FIG. 1, 100; FIG. 2, 200) may be pushed past a number ofpre-loaded retention dogs (1400). These retention dogs (1400) aredisposed so as to allow passage of the molds (FIG. 1, 100; FIG. 2, 200)in an upwards direction, but once a mold (FIG. 1, 100; FIG. 2, 200) isclear of the retention dogs (1400), a number of springs (1405) mayprovide sufficient force to cause the retention dogs (1400) to moveradially inwards, where they form a seat on which the last introducedmold (FIG. 1, 100; FIG. 2, 200) sits, thus holding the molds (FIG. 1,100; FIG. 2, 200) within the curing zone (610). In one embodiment, themolds (FIG. 1, 100; FIG. 2, 200) may include a number of engagementapertures or gas diffusion apertures (FIG. 1; 130) which may be providedso that the retention dogs (1400) may engage the molds (FIG. 1, 100;FIG. 2, 200) and secure the molds (FIG. 1, 100; FIG. 2, 200) in both thehorizontal and vertical directions. This may ensure that the molds (FIG.1, 100; FIG. 2, 200) may remain in a fixed position with respect to therotatable tube (400). In yet another embodiment, the engagementapertures (FIG. 1; 130) may fully surround the retention dogs (1400)such that the engagement apertures (FIG. 1; 130) are not open at thebottom of the molds (FIG. 1, 100; FIG. 2, 200). This may help to furthersecure the molds (FIG. 1, 100; FIG. 2, 200) within the rotatable tube(400). As mentioned above, the rotatable tube (400) may include a numberof retention dogs (1400) to secure every mold (FIG. 1, 100; FIG. 2, 200)in a fixed position within the rotatable tube (400).

In another embodiment, there may be provided retention dogs (1400) atthe lower end of the rotatable tube (400) so as to provide a seat forthe last mold (FIG. 1, 100; FIG. 2, 200) introduced into the rotatabletube (400). Thus, only the bottom mold (FIG. 1, 100; FIG. 2, 200) willmechanically engage with the rotatable tube (400). The remainingengagement apertures (FIG. 1; 130) may be used to allow for diffusion ofgas throughout the rotatable tube (400) and between the number of molds(FIG. 1, 100; FIG. 2, 200).

The molds (FIG. 1, 100; FIG. 2, 200) may be introduced individually, oras a stacked column of molds. In yet another embodiment, the pusher roditself may serve as the means for holding the molds (FIG. 1, 100; FIG.2, 200) within the curing zone (610) of the rotatable tube (400). Thiscan prove to be advantageous in terms of process time and simplicity aswell as simplicity in the manufacturing, use and maintenance of thecontact lens manufacturing system (FIG. 13, 1300).

Exemplary Operation

In one preferred mode of operation, inert gas is passed into the housing(1005) via the gas inlet ports (FIG. 13, 1310). The molds (FIG. 1, 100;FIG. 2, 200), dosed with a polymerizable liquid, are then introducedinto the stationary rotatable tube (400) through the lower end using apusher rod. The molds are either introduced individually or as a stackedcolumn. The pusher rod lifts the molds past the retention dogs (FIG. 13,1300) and is then withdrawn. The lowest mold in the stack of molds thensits on the retention dogs (FIG. 13, 1300). The drive mechanism for therotatable tube (FIG. 4, 400; FIG. 7, 700; FIG. 8, 800; FIG. 9, 900) isthen turned on, and the rotatable tube (400) is then rotated at apredetermined speed. In this state, the centrifugal force created by therotation of the rotatable tube (400) acts upon the polymerizable liquid,pushing it out towards the edges of the molding cavity (FIG. 1, 120) ofeach mold (FIG. 1, 100; FIG. 2, 200). The rotatable tube (400) isrotated at this predetermined speed for a period of time to allow theconcave surface (produced by the combination of factors such as speed ofrotation, surface tension of the polymerizable liquid, and accelerationdue to gravity) to reach its equilibrium shape. At this point, thecolumn of molds (FIG. 1, 100; FIG. 2, 200) is illuminated by actinicradiation thus initiating its polymerization and formation of the solidarticle. At completion of the curing process, the actinic radiation isextinguished and the rotation of the rotatable tube (400) is stopped.The cured molds (FIG. 1, 100; FIG. 2, 200) can then be removed byraising the pusher rod and pushing the cured molds (FIG. 1, 100; FIG. 2,200) from the top of the rotatable tube (400) for collection.

While the use of metal rotatable tubes has been proposed for the spincasting of contact lenses (See, for example, the '138 Patent), it isapparent that such tubes would preclude the use of ultraviolet light (orother similar radiation) to initiate polymerization. However, byadopting the simple expedient of placing apertures into the walls of therotatable tube, it has proved possible to produce robust equipment forthe manufacture of high quality contact lenses. The shape anddisposition of the apertures is selected to optimize light transmissioninto the tube, while maintaining a physically robust structural form.The apertures also allow for rapid and homogenous gas exchange from thecontact lens molds so as to provide an inert atmosphere above thepolymerizable liquid, thus reducing the deleterious effects of oxygeninhibition.

The design of rotatable tube described herein, particularly when coupledto an outer casing provides for an easily interchangeable, mechanicallyrobust apparatus for the spin casting of rotationally symmetric objectssuch as contact lenses, which requires very little or no maintenance inuse.

Multi-Stage Curing

FIG. 15 is a flow chart of a multi-stage curing process according to anembodiment of the present exemplary system and method. After curing orpartial curing of the polymerizable liquid, the molds may then be pushedupwards using the pusher rod into a secondary curing device placed ontop of the rotatable tube (400). Alternatively, the molds may beoffloaded manually, or by a robot arm. The secondary curing device maythen further cure the polymerizable liquid contained within the molds.The secondary curing device may be any device traditionally employed.For example, the secondary curing device may be a traditional glasstube.

Turning now in more detail to FIG. 15, in one embodiment, the moldscontaining the polymerizable liquid may be introduced to the rotatabletube (400) as described above (Step 2110). Next, a partial curing of thelens polymer via illumination by actinic radiation takes place withinthe rotatable tube (400), thereby initiating its polymerization andpartial formation of the solid article (Step 2120). Therefore, accordingto this exemplary embodiment, the initial cross-linking of the lens maybe performed within the curing zone (FIG. 6, 610) of the rotatable tube(400).

During the initial stages of the curing of the lens, the polymer is mostsusceptible to the introduction of imperfections in the surface of theresulting lens. Vibrations resulting in movement of the mold or standingwaves, which produce poor optics, occur when the lens material is mostfluidic. Consequently, according to one exemplary embodiment, a lens ispartially formed within the curing zone (FIG. 6, 610) of the rotatabletube (400) to a degree where the shape of the contact lens isestablished and stable. The lens and lens mold combination is thentransferred to a traditional glass tube or another less controlledenvironment for final curing. That is, according to this exemplaryembodiment, in order to assure that vibrations and run-out areminimized, the lens is initially rotated, illuminated, and cross-linkedin the controlled environment of the rotatable tube (400) as taughtherein. Specifically, the tighter tolerances of the present exemplaryrotatable tube (400) along with the other features including, but in noway limited to, reduced run-out and de-coupled magnetic drive, result inan initial form of the lens with minimal surface aberrations.

Returning now to FIG. 15, with the shape and surface area of the lensestablished, the partially formed lens may be transferred from therotatable tube (400) to a secondary curing tube (Steps 2130 and 2140),where the partially formed lens may be fully cured (Step 2150). Thecuring of the lens may be concluded in the secondary curing tube via anymeans including, but in no way limited to, photochemical or thermalinduced polymerization. Further, in another exemplary embodiment, thesecond stage curing of the partially formed lens may occur in a suitablycontrolled tunnel oven which may finalize the curing of the lens viaeither actinic radiation, heat, or both. Once an initial amount ofcross-linking has occurred via actinic radiation within the rotatabletube (400), the partially cross-linked lens polymer has sufficientstructural stability to be less affected or entirely unaffected byrotation in the secondary curing tube or through introduction to theabove-mentioned tunnel oven or other curing device.

Further, through the employment of the above-described multi-stagecuring process, the time required to produce a fully cured article maybe significantly reduced. The time required to partially cure an articlewithin the rotatable tube (400) may take only a short amount of time.Through simple division of resources, the time required to produce afinished article may divided between the first partial curing stageusing the rotatable tube (400) and the second fully curing stage usingthe secondary curing tube. Still further, multiple secondary curingtubes may be provided to allow even more articles partially cured withinthe rotatable tube (400) to be fully cured in the multiple secondarycuring tubes.

The preceding description has been presented only to illustrate anddescribe embodiments and examples of the principles described. Thisdescription is not intended to be exhaustive or to limit theseprinciples to any precise form disclosed. Many modifications andvariations are possible in light of the above teaching.

The invention claimed is:
 1. A method of centrifugally casting a lens,comprising: providing a first rotatable tube having a first end and asecond end connected by a longitudinal outside surface that defines aninterior longitudinal cavity configured to receive at least one contactlens mold; introducing at least one mold into the internal longitudinalcavity of the first rotatable tube, the at least one mold containing apolymerizable liquid; at least partially curing the polymerizable liquidin the first rotatable tube via actinic radiation while rotating thetube; wherein the first rotatable tube includes at least one portiondefining at least one aperture, wherein the at least one apertureextends from the interior longitudinal cavity to the longitudinaloutside surface of the first rotatable tube, and the at least oneaperture is configured to permit the transmission of actinic radiationinto the interior longitudinal cavity during rotation of the tube, saidat least one portion being at least partially made of material that isopaque to actinic radiation.
 2. The method of claim 1, furthercomprising rotating the first rotatable tube such that the polymerizableliquid contained within the at least one mold forms a concave shape. 3.The method of claim 1, further comprising exposing the polymerizableliquid to actinic radiation through the at least one aperture.
 4. Themethod of claim 1, wherein: the first rotatable tube further comprises afirst bearing mounting zone formed on the first end of the firstrotatable tube and a second bearing mounting zone formed on the secondend of the first rotatable tube; wherein the first bearing mounting zoneand the second bearing mounting zone are each constructed of an opaquematerial configured to withstand high tensile stresses.
 5. The method ofclaim 1, wherein at least partially curing the polymerizable liquid inthe first rotatable tube while rotating the tube further comprisesdiffracting actinic radiation entering the first rotatable tube whilerotating the tube.
 6. The method of claim 1, wherein at least partiallycuring the polymerizable liquid in the first rotatable tube whilerotating the tube further comprises reflecting actinic radiationentering the first rotatable tube while rotating the tube.
 7. The methodof claim 1, further comprising: removing the at least one mold from thefirst rotatable tube; providing at least one second curing device;introducing the at least one mold into the at least one second curingdevice; and further curing of the polymerizable liquid in the at leastone second curing device.
 8. The method of claim 7, further comprisingpartially curing the polymerizing liquid in the at least one mold untila shape and surface area of the lens is established.
 9. A method ofcentrifugally casting a lens, comprising: providing a first rotatabletube having a first end and a second end connected by a longitudinaloutside surface that defines an interior longitudinal cavity configuredto receive at least one contact lens mold; introducing at least one moldinto the internal longitudinal cavity of the first rotatable tube, theat least one mold containing a polymerizable liquid; at least partiallycuring the polymerizable liquid in the first rotatable tube via actinicradiation while rotating the tube; wherein the first rotatable tubeincludes at least one portion defining at least one aperture, whereinthe at least one aperture extends from the interior longitudinal cavityto the longitudinal outside surface of the first rotatable tube, and theat least one aperture is configured to permit the transmission ofactinic radiation into the interior longitudinal cavity during rotationof the tube, said at least one portion being at least partially made ofa metal.
 10. The method of claim 9, further comprising rotating thefirst rotatable tube such that the polymerizable liquid contained withinthe at least one mold forms a concave shape.
 11. The method of claim 9,further comprising exposing the polymerizable liquid to actinicradiation through the at least one aperture.
 12. The method of claim 9,wherein the first rotatable tube further comprises a first bearingmounting zone formed on the first end of the first rotatable tube and asecond bearing mounting zone formed on the second end of the firstrotatable tube; wherein the first bearing mounting zone and the secondbearing mounting zone are each constructed of a metal configured towithstand high tensile stresses.
 13. The method of claim 9, wherein atleast partially curing the polymerizable liquid in the first rotatabletube while rotating the tube further comprises diffracting actinicradiation entering the first rotatable tube through the at least oneaperture while rotating the tube.
 14. The method of claim 9, wherein atleast partially curing the polymerizable liquid in the first rotatabletube while rotating the tube further comprises reflecting actinicradiation entering the first rotatable tube through the at least onepaerture while rotating the tube.
 15. The method of claim 9, furthercomprising: removing the at least one mold from the first rotatabletube; providing at least one second curing device; introducing the atleast one mold into the at least one second curing device; and furthercuring of the polymerizable liquid in the at least one second curingdevice.
 16. The method of claim 15, further comprising partially curingthe polymerizing liquid in the at least one mold until a shape andsurface area of the lens is established.
 17. A method of centrifugallycasting a lens, comprising: providing a first rotatable tube having afirst end and a second end connected by a longitudinal outside surfacethat defines an interior longitudinal cavity configured to receive atleast one contact lens mold; introducing at least one mold into theinternal longitudinal cavity of the first rotatable tube, the at leastone mold containing a polymerizable liquid; at least partially curingthe polymerizable liquid in the first rotatable tube while rotating thetube; wherein the first rotatable tube includes at least one portiondefining at least one aperture, wherein the at least one apertureextends from the interior longitudinal cavity to the longitudinaloutside surface of the first rotatable tube, and the at least oneaperture is configured to permit the transmission of actinic radiationinto the interior longitudinal cavity during rotation of the tube, saidat least one portion being at least partially made of a material that isopaque to actinic radiation.